Recycling of flexible foam

ABSTRACT

Process for recycling flexible foams by glycolysis and extraction. The glycolysis is conducted by allowing the foam to react with low molecular weight polyols, then allowing the mixture to separate in two phases.

The present invention is concerned with the recycling of flexiblepolyurethane foams, with the products obtained by this recyclingprocess, with prepolymers made from products obtained by this recyclingprocess and with processes for preparing useful polyurethane productsfrom said prepolymers and said products obtained by this recyclingprocess.

The re-use of plastics and polyurethane foams in particular has beendescribed extensively in the past and consists mainly of energyrecovery, physical recycling and chemical depolymerisation.

Chemical depolymerisation of polyurethanes may be achieved, amongstother processes, by hydrolysis, aminolysis, glycolysis andhydroglycolysis. Such processes have been described widely in the art,see e.g. U.S. Pat. Nos. 3,632,530, 3,708,440, 4,159,972, 3,404,103,3,300,417, 2,937,151, 4,316,992 and European Patent Application 546415.

In the context of the present invention the following terms have thefollowing meaning:

1) isocyanate index or NCO index or index: the ratio of the number ofNCO-groups over the number of isocyanate-reactive hydrogen atoms presentin a formulation, given as a percentage: ##EQU1##

In other words the NCO-index expresses the percentage of isocyanateactually added to a formulation with respect to the amount of isocyanatetheoretically required for reacting with the amount ofisocyanate-reactive hydrogen used in a formulation.

It should be observed that the isocyanate index as used herein isconsidered from the point of view of the actual foaming processinvolving the isocyanate ingredient and the isocyanate-reactiveingredients. Any isocyanate groups consumed in a preliminary step toproduce modified polyisocyanates (including such isocyanate-derivativesreferred to in the art as quasi or semi-prepolymers and prepolymers) orany active hydrogens reacted with isocyanate to produce modified polyolsor polyamines, are not taken into account in the calculation of theisocyanate index. Only the free isocyanate groups and the freeisocyanate-reactive hydrogens (including those of the water, if used)present at the actual foaming stage are taken into account.

2) The expression "isocyanate-reactive hydrogen atoms" as used hereinfor the purpose of calculating the isocyanate index refers to the totalof hydroxyl and amine hydrogen atoms present in the reactivecompositions in the form of polyols, polyamines and/or water; this meansthat for the purpose of calculating the isocyanate index at the actualfoaming process one hydroxyl group is considered to comprise onereactive hydrogen, one primary amine group is considered to comprise onereactive hydrogen and one water molecule is considered to comprise twoactive hydrogens.

3) Reaction system: a combination of components wherein thepolyisocyanate component is kept in a container separate from theisocyanate-reactive components.

4) The expression "polyurethane foam" as used herein generally refers tocellular products as obtained by reacting polyisocyanates withisocyanate-reactive hydrogen containing compounds, using foaming agents,and in particular includes cellular products obtained with water asreactive foaming agent (involving a reaction of water with isocyanategroups yielding urea linkages and carbon dioxide and producingpolyurea-urethane foams).

5) The term "(average nominal) hydroxyl functionality" is used herein toindicate the average functionality (number of hydroxyl groups permolecule) of the polyol composition on the assumption that this is theaverage functionality (number of active hydrogen atoms per molecule) ofthe initiator(s) used in their preparation although in practice it willoften be somewhat less because of some terminal unsaturation.

6) The term "high molecular weight polyol" refers to polyols preferablypolyether polyols, most preferably polyoxyethylene polyols,polyoxypropylene polyols and polyoxyethylene polyoxypropylene polyols,which polyols have an average nominal hydroxyl functionality of 2-6 anda number average equivalent weight of 500-5000.

7) The term "alcoholising polyol" refers to those polyols which are ableto alcoholise flexibe polyurethane foams and which are immiscible withthe high molecular weight polyol obtained in the alcoholysis process;wherein immiscible means that at most 30%, preferably at most 20% byweight of alcoholising polyol can be dissolved in the high molecularweight polyol at room temperature.

Surprisingly we have found that flexible polyurethane foams may bealcoholised in such a way that two products are obtained, the firstproduct (hereinafter called product 1) being a high molecular weightpolyol which after purification has properties equivalent to theoriginally used high molecular weight polyol and which can be used againcompletely to make a recycled flexible foam having properties similar tothe original flexible foam and the second product (hereinafter calledproduct 2) being a product comprising urethane groups which productafter purification and/or further chemical treatment may be used indifferent useful ways.

Consequently the present invention is concerned with a process foralcoholizing a flexible polyurethane foam by bringing the foam incontact with an alcoholizing polyol, preferably selected from glyceroland an oxyethylene polyol having a molecular weight of 62-500 andmixtures thereof, allowing the foam and the polyol to react, thenallowing the mixture to separate in an upper and a lower phase andsubsequently collecting these two phases in separate containers. Theupper phase contains predominantly a polyol having a high molecularweight (product 1) and the lower phase contains predominantlyalcoholizing polyol and products having a low molecular weightcomprising urethane, amine and hydroxyl groups (product 2).

The flexible polyurethane foam starting material is a foam made byreacting a polyisocyanate and a polyol having a high molecular weightusing a blowing agent and optionally a chain extender or cross-linkerand additives conventionally used in preparing flexible polyurethanefoams. Such foams, ingredients used for preparing the foams andprocesses for preparing such foams have been described extensively inthe art, see e.g. European Patent Publications 10850, 22617, 296449,309217, 309218, 392788, 442631 and 480588. Organic polyisocyanates usedfor making such flexible foams may be selected from aliphatic,cycloaliphatic and araliphatic polyisocyanates, especiallydiisocyanates, like hexamethylene diisocyanate, isophorone diisocyanate,cyclohexane-1,4-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate andm- and p- tetramethylxylylene diisocyanate, and in particular aromaticpolyisocyanates like tolylene diisocyanates (TDI), phenylenediisocyanates and most preferably methylene diphenyl isocyanates havingan isocyanate functionality of at least two. The methylene diphenylisocyanates (MDI) may be selected from pure 4,4'-MDI, isomeric mixturesof 4,4'-MDI and 2,4'-MDI and less than 10% by weight of 2,2'-MDI, crudeand polymeric MDI having isocyanate functionalities above 2, andmodified variants thereof containing carbodiimide, uretonimine,isocyanurate, urethane, allophanate, urea or biuret groups. Mostpreferred methylene diphenyl isocyanates are pure 4,4'-MDI, isomericmixtures with 2,4'-MDI optionally containing up to 50% by weight ofpolymeric MDI and uretonimine and/or carbodiimide modified MDI having anNCO content of at least 25% by weight and urethane modified MDI obtainedby reacting excess MDI and a low molecular weight polyol (MW less than999) and having an NCO content of at least 25% by weight. Mixtures ofmethylene diphenyl isocyanates with up to 25% by weight of otherpolyisocyanates mentioned above may be used if desired.

The polyisocyanate may contain dispersed urea particles and/or urethaneparticles prepared in a conventional way, e.g. by adding a minor amountof an isophorone diamine to the polyisocyanate. The high molecularweight polyols used for preparing such flexible foams may be selectedfrom polyesters, polyesteramides, polythioethers, polycarbonates,polyacetals, polyolefins, polysiloxanes and, especially, polyethers.Polyether polyols which may be used include products obtained by thepolymerisation of a cyclic oxide, for example ethylene oxide, propyleneoxide, butylene oxide or tetrahydrofuran in the presence, wherenecessary, of polyfunctional initiators. Suitable initiator compoundscontain a plurality of active hydrogen atoms and include water,butanediol, ethylene glycol, propylene glycol, diethylene glycol,triethylene glycol, dipropylene glycol, ethanolamine, diethanolamine,triethanolamine, toluene diamine, diethyl toluene diamine, phenyldiamine, diphenylmethane diamine, ethylene diamine, cyclohexane diamine,cyclohexane dimethanol, resorcinol, bisphenol A, glycerol,trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol, sorbitol andsucrose. Mixtures of initiators and/or cyclic oxides may be used.Especially useful polyether polyols include polyoxypropylene diols andtriols and poly(oxyethylene-oxypropylene) diols and triols obtained bythe simultaneous or sequential addition of ethylene and propylene oxidesto di- or trifunctional initiators as fully described in the prior art.Random copolymers having oxyethylene contents of 10-80%, blockcopolymers having oxyethylene contents of up to 25% and random/blockcopolymers having oxyethylene contents of up to 50%, based on the totalweight of oxyalkylene units may be mentioned, in particular those havingat least part of the oxyethylene groups at the end of the polymer chain.Mixtures of the said diols and triols can be particularly useful. Otherparticularly useful polyether polyols include polytetramethylene glycolsobtained by the polymerisation of tetrahydrofuran. Polyester polyolswhich may be used include hydroxyl-terminated reaction products ofpolyhydric alcohols such as ethylene glycol, propylene glycol,diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol,cyclohexane dimethanol, glycerol, trimethylolpropane, pentaerythritol orpolyether polyols or mixtures of such polyhydric alcohols, andpolycarboxylic acids, especially dicarboxylic acids or theirester-forming derivatives, for example succinic, glutaric and adipicacids or their dimethyl esters, sebacic acid, phthalic anhydride,tetrachlorophthalic anhydride or dimethyl terephthalate or mixturesthereof. Polyesters obtained by the polymerisation of lactones, forexample caprolactone, in conjunction with a polyol, or of hydroxycarboxylic acids such as hydroxy caproic acid, may also be used.Polyesteramides may be obtained by the inclusion of aminoalcohols suchas ethanolamine in polyesterification mixtures. Polythioether polyolswhich may be used include products obtained by condensing thiodiglycoleither alone or with other glycols, alkylene oxides, dicarboxylic acids,formaldehyde, amino-alcohols or aminocarboxylic acids. Polycarbonatepolyols which may be used include products obtained by reacting diolssuch as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethyleneglycol or tetraethylene glycol with diaryl carbonates, for examplesdiphenyl carbonate, or with phosgene. Polyacetal polyols which may beused include those prepared by reacting glycols such as diethyleneglycol, triethylene glycol or hexanediol with formaldehyde. Suitablepolyacetals may also be prepared by polymerising cyclic acetals.Suitable polyolefin polyols include hydroxy-terminated butadiene homo-and copolymers and suitable polysiloxane polyols includepolydimethylsiloxane diols and triols. Other polyols which may be usedcomprise dispersions or solutions of addition or condensation polymersin polyols of the types described above. Such modified polyols, oftenreferred to as "polymer" polyols have been fully described in the priorart and include products obtained by the in situ polymerisation of oneor more vinyl monomers, for example styrene and/or acrylonitrile, inpolymeric polyols, for example polyether polyols, or by the in situreaction between a polyisocyanate and an amino- and/orhydroxy-functional compound, such as triethanolamine, in a polymericpolyol. Polyoxyalkylene polyols containing from 5 to 50% of dispersedpolymer are particularly useful. Particle sizes of the dispersed polymerof less than 50 microns are preferred. The number average equivalentweight of the high molecular weight polyols preferably is 750-3000; theaverage nominal hydroxyl functionality preferably is 2-4; the hydroxylvalue preferably ranges from 15-200 and most preferably from 20-100. Thechain-extending and cross-linking agents which optionally may be used inpreparing such foams may be selected from amines and polyols containing2-8 and preferably 2-4 amine and/or hydroxy groups like ethanolamine,diethanolamine, triethanolamine, ethylene glycol, diethylene glycol,triethylene glycol, propylene glycol, dipropylene glycol, butanediol,glycerol, trimethylolpropane, pentaerithrithol, sorbitol, sucrose,polyethylene glycol having an equivalent weight of less than 500,toluene diamine, diethyl toluene diamine, cyclohexane diamine, phenyldiamine, diphenylmethane diamine, an alkylated diphenylmethane diamineand ethylene diamine. The amount of chain-extending and cross-linkingagents is, if applied, up to 25 and preferably up to 10 parts by weightper 100 parts by weight of the high molecular weight polyol. The blowingagent may be selected from physical blowing agents likechlorofluorocarbons, hydrogen chlorofluorocarbons, hydrogenfluorocarbons and preferably from chemical blowing agents, especiallythose which lead to CO₂ liberation when reacted with the polyisocyanateunder foam forming conditions. Most preferably water is used as the soleblowing agent. The amount of water may range from 2-20 preferably from3-15 parts by weight per 100 parts by weight of isocyanate-reactivecompound having a number average equivalent weight of 500 to 5000. Theauxiliaries and additives which amongst others may be used are formationof urea and urethane enhancing catalysts like tertiary amines,imidazoles and tin compounds, surfactants, stabilisers, flameretardants, fillers and anti-oxidants. They may be premixed with theisocyanate-reactive materials before these materials are reacted withthe polyisocyanate in order to prepare the foams. The foams may be madeaccording to the one-shot process, the semi- or quasi prepolymer processor the prepolymer process. The foams may be slab-stock or mouldedflexible foams. The foams in general have a density of 15-80 kg/m³ andmay have been used as cushioning material in furniture, car-seats andmattresses for instance.

Although in principle any such flexible polyurethane foam may be used inthe process according to the present invention, MDI-based, polyetherpolyol-based, fully water blown flexible polyurethane foams areparticularly preferred in view of the very good results obtained, aswill be described hereinafter. Amongst these particularly preferredfoams, those prepared according to the prepolymer process as describedin EP 392788 are even further preferred.

The flexible foam may be combined with the alcoholizing polyol in theform in which it is received but preferably the size of the foam piecesis reduced, if necessary, in a way suitable for reducing the size and/orfor increasing the density of foam pieces, like by cutting, milling,pelletizing, grinding, comminution, densification and pressing andcombinations thereof. Although the success of the process of the presentinvention does not greatly depend on the size of the foam pieces it isfor efficiency and handling reasons preferred to have pieces having anaverage diameter between 0.1 mm and 10 cm.

The alcoholizing polyol preferably is selected from glycerol and anoxyethylene polyol having a molecular weight of 62-500 which may have ahydroxyl functionality of 2-8, and may be selected from ethylene glycoland polyols prepared by reacting ethylene oxide with an initiator havinga hydroxyl functionality of 2-8 like ethylene glycol, glycerol,trimethylol propane, pentaerythritol and sorbitol. Preferably thehydroxyl functionality is 2. Most preferably the alcoholizing polyol isethylene glycol or diethylene glycol or a mixture thereof.

The foam or foam pieces and the alcoholizing polyol are combined,suitably by normal mixing in a container suitable to conduct aalcoholysis reaction process. The alcoholysis reaction conditions arechosen in such a way that the alcoholysis reaction reaches equilibriumin a reasonable period of time. Generally the pressure applied rangesfrom ambient pressure to 10 bar, preferably from ambient pressure to 5bar and most preferably the process is conducted at ambient pressure,and the reaction temperature ranges from 170° to 240° C., preferablyfrom 180° to 220° C. and the reaction time from 0.5 to 8 hours,preferably from 1 to 6 hours. The reaction preferably is conducted whilestirring and under a N₂ blanket. The relative amounts of the foam andthe polyol generally will range from 0.1 to 10 parts by weight (pbw) ofpolyol per pbw of foam and preferably from 0.5 to 5 pbw. If desiredwater may be present in an amount of up to 5% by weight on foam andpolyol. If desired other reactive ingredients like alkanol amines may bepresent in an amount of up to 5% by weight on foam and polyol. Ifdesired a catalyst enhancing the alcoholysis of the foam may be usedlike tetrabutyltitanate, potassium acetate, dimethylimidazole and ingeneral urethane-reaction promoting catalysts.

After the mixing is stopped, the mixture is left for a period sufficientto allow the mixture to separate in two phases. Generally a periodranging from 1 minute to 24 hours will be sufficient. Preferably thisperiod is 15 minutes to 4 hours.

After stirring has been discontinued the temperature may be maintainedwhile the phases are allowed to separate and when the phases arecollected. Alternatively the temperature may be reduced by cooling or byno longer supplying heat after stirring has been discontinued or afterphase separation but before collecting the phases.

The upper phase predominantly comprises the high molecular weight polyolfrom which the foam was made (product 1) and the lower phasepredominantly comprises the other chemicals obtained (product 2)together with the alcoholizing polyol.

The both products are then collected separately in a conventional way,e.g. by decanting the upper phase or by removing the lower phase via anoutlet in the bottom of the container. Sometimes an interface may bepresent after phase separation between the upper and the lower phase,which interface may be collected separately or together with either ofthe two phases.

The process may be conducted batchwise or continuously.

The present invention is also concerned with products 1 and 2 soobtainable.

Then product 1 is subjected to an extraction process which comprisesbringing the polyol (product 1) into contact with an extracting compoundwhich is a polyol or a polyol mixture having a number average molecularweight of at most 500 and being immiscible with the polyol (product 1),mixing the extracting compound and the polyol, allowing the extractingcompound and the polyol to separate and removing the extractingcompound.

This extraction process reduces the level of amines in product 1 whichamines were formed during the previous alcoholizing step, in particularthe level of aromatic amines like toluene diamine and diaminodiphenylmethane and higher functional oligomers thereof. In addition itreduces the level of polyoxyalkylene polymeric material having allylicunsaturation at the end of the polymer chain in those cases where theflexible foam was made from polyether polyols having a higher molecularweight and comprising a higher level of unsaturation, e.g. more than0.03 meq/g, like most presently commercial polyether polyols having ahigh molecular weight and an oxypropylene content of more than 30% byweight which in general have a level of unsaturation of 0.04-0.10 meq/g.The extraction process further reduces the level of compounds containingurethane and urea groups.

The reduction in unsaturation obtainable will depend inter alia upon thelevel of unsaturation present in the starting material, the extractingcompound selected and the number of extraction steps applied. Byapplying the extraction process the unsaturation may be reduced by atleast 10% of its original value; by applying the extraction processbatchwise more than once, e.g. 5 or 6 times, or continuously theunsaturation may be reduced by 50% of its original value or more.

The extracting compounds preferably are selected from the groupconsisting of ethylene glycol, diethylene glycol, triethylene glycol,tetraethylene glycol, glycerol and butanediol and mixtures thereof;ethylene glycol and diethylene glycol and mixtures thereof being mostpreferred.

Immiscibility in the context of the present invention is defined asfollows: an extracting compound is considered as immiscible if at most30% preferably at most 20% by weight of extracting compound can bedissolved in product 1 at room temperature.

The extraction process is carried out as a conventional extractionprocess. It may be carried out batchwise or continuously. If the processis carried out batchwise this may be done once or preferably at leasttwo and more preferably 2-15 times. The extraction process may beconducted at room temperature or at elevated temperature provided thetemperature applied is lower than the boiling point of the extractingcompound under the conditions applied and than the temperature at whichthe polyol (product 1) would disintegrate under the conditions applied.In general the temperature may range from ambient temperature to 240° C.but preferably is 150°-240° C. and most preferably 180°-220° C. atambient pressure-10 bar, preferably ambient pressure -5 bar, mostpreferably at ambient pressure. Once the polyol (product 1) and theextracting compound have been combined they are mixed. The amount ofextracting compound used may vary between wide ranges. Preferably theweight ratio of extracting compound and polyol is at least 0.1:1 andmost preferably 0.25-10:1. If desired water may be present in an amountof up to 5% by weight calculated on the weight of product 1 andextracting compound. The mixing preferably is continued for a period oftime of from 1 minute to 8 hours, more preferably from 5 minutes to 3hours preferably under a N₂ blanket.

After the mixing is discontinued the mixture is left in order to allowthe mixture to separate in two phases, then the phases are collected.Phase separation and the collection of the phases is conductedessentially in the same way as described above after the acoholysisstep. The extraction process may be integrated with the acoholysis in abatchwise way or in a continuous process.

The present invention is also concerned with the polyol obtainable afterthis extraction process (product 3). Product 3 may be further purified,if desired, in order to remove remaining extracting compound, e.g. byevaporation which is conducted in a conventional way at a temperaturebelow the boiling point of the high molecular weight polyol and/or byfiltration. In general the evaporation conditions are as follows:temperature 120° to 200° C., preferably from 150°-180° C., time 0.25 to10 hours, preferably 1 to 5 hours and pressure 0.1 to 100 mbar,preferably 0.1 to 10 mbar. Further extraction/evaporation steps may beconducted if desired.

After evaporation a polyol is obtained which hereinafter will bereferred to as product 4. This evaporation may be integrated with thealcoholysis and the extraction process in a batchwise-way or in acontinuous process. The present invention is also concerned with thepolyol obtainable after this evaporation process.

Product 4 has properties which are very similar to the properties of thepolyols having a high molecular weight which were originally used formaking the flexible foam. In case the polyol having a high molecularweight originally used in the flexible foam was a polyether polyolhaving a higher level of unsaturation, the properties of product 4 areeven better since the level of unsaturation is lower.

Because of these similar or even better properties product 4 isparticularly useful for re-use in the preparation of flexible foams. Upto 100% of product 4 may be re-used, which means that no polyol having ahigh molecular weight other than product 4 is necessary for preparing anew flexible foam. The foams are made in a conventional way.

The foams are made by reacting a polyisocyanate with product 4 andoptionally with freshly prepared polyol having a high molecular weightand optionally with chain extenders, cross-linkers and additivesconventionally used in preparing flexible foams and using a blowingagent, preferably water, at an isocyanate index of 40-120. The foams maybe made according to the one-shot, the semi-prepolymer and prepolymerprocess. The polyisocyanates, freshly prepared polyols, chain-extenders,cross-linkers and additives may be selected from those describedhereinbefore.

The present invention is further concerned with isocyanate-terminatedpolyurethane (semi)-prepolymers having an NCO value of 2-30, preferably5-20% by weight prepared by reacting an excess of hydroxyl functionalityof 2-6, a number average equivalent weight of 500-5000, an unsaturationlevel of less than 0.03 meq/g, preferably 0.005-0.02 meq/g, andpreferably an oxypropylene content of at least 30% by weight, morepreferably at least 50% by weight, most preferably at least 70% byweight. The polyols used in preparing these prepolymers can be made byextracting a polyol having a higher degree of unsaturation followed byevaporation as described hereinbefore. These polyols contain afterevaporation 0.01-0.5% by weight of the extracting compound; such polyolsare polyols according to the present inventions as well; the hydroxylvalue of such polyols (mg KOH/g) does not differ more than 20% from thevalue of the polyol used in the recycled flexible foam. Thepolyisocyanate and polyols used may be selected from those describedhereinbefore.

Although there is still some extracting compound present in the polyoland although the level of unsaturation in the polyol is lower,prepolymers made from such polyols surprisingly show only a limitedviscosity increase (less than 100%, preferably less than 50%) comparedwith the prepolymer from which the recycled foam was made and althoughthere is still some extracting compound present the flexible foams madefrom such prepolymers nevertheless show an improved compression set andalthough the level of unsaturation is lowered the tear strength of thefoam may be improved; the other physical properties of the foam beingsimilar (hardness, hysteresis loss, elongation, resilience); comparedwith the original foam.

The prepolymer is prepared conventionally, as described in e.g. EP392788, 10850 and 22617.

Still further the present invention is concerned with a process forpreparing a flexible foam by reacting the above prepolymer with water atan isocyanate index of 40-120, optionally in the presence of chainextenders, cross-linkers and additives conventionally used in preparingflexible foams.

Further the present invention is concerned with isocyanate-terminatedpolyurethane (semi)-prepolymers having an NCO value of 2-30% by weightprepared by reacting an excess of polyisocyanate with product 4 and witha process for preparing a flexible foam using such a (semi)-prepolymeras polyisocyanate. In case a prepolymer is used the foams are made byreacting the prepolymer with water at an isocyanate index of 40-120,optionally in the presence of chain extenders, cross-linkers andadditives conventionally used for preparing flexible foams. In case asemi-prepolymer is used the foams are made by reacting at an isocyanateindex of 40-120 the semi-prepolymer with product 4 and/or with a freshlyprepared polyol having a high molecular weight using a blowing agent,preferably water, and optionally using chain extenders, cross-linkersand additives conventionally used in preparing a flexible foam. Thepolyisocyanate used for preparing the (semi)-prepolymer, the freshlyprepared polyol, chain-extenders, cross-linkers and additives may beselected from those mentioned hereinbefore.

Product 2 predominantly comprises lower molecular weight compoundscomprising urethane, amine and/or hydroxyl groups.

Product 2 may, after alkoxylation, in particular propoxylation, andpurification, in particular evaporation, be used in the preparation ofpolyurethane foams, in particular rigid polyurethane foams. Thealkoxylation is applied in order to react away the active hydrogencontaining amine groups, in particular aromatic diamines like toluenediamines and diphenylmethane diamines. Alkoxylation is conducted in aconventional way. The product obtained after alkoxylation has anhydroxyl value of 300 to 1000 mg KOH/g. After alkoxylation the productmay be subjected to evaporation to give a product having an hydroxylvalue of 250 and 600 mg KOH/g. The alkoxylation and purification ofproduct 2 may also be conducted in the reverse order.

The invention is illustrated by the following examples:

Example 1

A flexible foam was made by reacting 10 parts by weight of prepolymer(prepared by reacting 9.6 pbw of a polymeric MDI having an isocyanatefunctionality of 2.7 and an NCO value of 30.7% by weight and 0.4 pbw ofa trifunctional polyoxyethylene polyoxypropylene polyol having 75%randomly distributed oxyethylene units and a molecular weight of 4000)and 90 pbw of a prepolymer (prepared by reacting 22.5 pbw of MDIcontaining 10% of 2,2'+2,4'-MDI and 67.5 pbw of a glycerol basedpolyoxyethylene polyoxypropylene polyol having 15% tipped oxyethyleneunits and a molecular weight of 6000) with a composition containing 1.96parts by weight of water and 0.65 pbw of dimethyl imidazole.

The flexible foam so obtained was cut into pieces of about 10×10×50 cm.

56.9 kg of the foam pieces so obtained were added to 60.1 kg of stirreddiethylene glycol, which was preheated at 180° C. and which contained41.5 g of tetrabutyltitanate. The mixture was kept under a N₂ blanket.Then the temperature was raised to 200° C. and the mixture was distilledfor 15 minutes, allowed to react for 2.5 hours and again distilled for15 minutes. During the distillation 4.5 kg of material was distilledoff. Then stirring was stopped and the mixture was allowed to phaseseparate while being cooled to 105° C. in 45 minutes. During 45 minutesthe bottom layer (61.7 kg) was drained off, followed by 2.9 kg ofinterface. The upper phase was 47.9 kg. To 70 kg of upper phase soobtained 49.8 kg of diethylene glycol was added and the mixture wasstirred, kept under N₂ and heated to 200° C. After 75 minutes stirringwas stopped and the mixture was cooled to 110° C. After 75 minutes thebottom layer was drained off (75.5 kg). This extraction procedure wasrepeated 6 times with 39.9, 23.4, 11.6, 11.5, 21.5 and 10.7 kg ofdiethylene glycol. The top layer then was heated to 195° C. over aperiod of 85 minutes and maintained at 195° C. for 15 minutes fordistillation. 28.2 kg of top-layer was obtained. 24.5 kg of this upperlayer was washed three times as described above with 30, 24.7 and 19.8kg of diethylene glycol followed by distillation at 190° C. for 3 hoursand filtration. The product so obtained is a polyether polyol having anOH value of 33 mg KOH/g containing 0.4% by weight of diethylene glycoland having an unsaturation value of 0.013 meq/g. Part of this polyol isused in example 4 hereinafter and is referred to as Polyol 1.

Example 2

Part of polyol 1 was further purified by wiped film evaporation (oiltemperature 180° C., pressure less than 5 mbar, N₂ purge. The polyolobtained--referred to as polyol 2 and used in example 4 hereinafter--hada diethylene glycol content of between 0.01 and 0.1% by weight and anunsaturation level of 0.014 meq/g.

Example 3

A conventional flexible foam used in car seats was glycolysed in a waysimilar to example 1. 5 kg of the bottom layer so obtained waspropoxylated by reaction with 125 g of propylene oxide (N₂ blanket, 50°C., mixing) for 8 hours which was repeated 3 times. Then the product waspurified by heating to 180° C. under vacuum. The product so obtained wasused in Example 6.

Example 4

An isocyanate-terminated polyurethane prepolymer was prepared by mixing25 pbw of MDI comprising 10% of 2,2'+2,4' MDI and 75 parts of a glycerolbased polyoxyethylene polyoxypropylene polyol having an oxyethylenecontent of 15% by weight (all tip), a molecular weight of 6000, anunsaturation value of about 0.08 meq/g, (the polyol did not containextracting compound) at a temperature of 85° C. for 4.5 hours. Theprepolymer has an NCO value of 6.7% by weight and a viscosity of 5600mPa.s (25° C.) (Prepolymer 1).

Prepolymer 2 was prepared as prepolymer 1 with the proviso that thepolyol was Polyol 1 obtained in example 1. The prepolymer had an NCOvalue of 6.6% by weight and a viscosity of 8000 mPa.s (25° C.).

Prepolymer 3 was prepared as prepolymer 1 with the proviso that thepolyol was Polyol 2 obtained in example 2. The prepolymer had an NCOvalue of 6.8% by weight and a viscosity of 6600 mPa.s (25° C.). Allviscosities were measured with a Brookfield viscosity measurementdevice.

Example 5

Foams were made by reacting 80 pbw of prepolymer 1, 2 or 3 made inexample 4 and 20 pbw of a prepolymer having an NCO value of 30% byweight, (which was made by reacting 98 pbw of polymeric MDI {NCO=30.7%by weight, isocyanate functionality=2.7} and 2 pbw of a polyol{trifunctional, molecular weight 4000, polyoxyethylene polyoxypropylenepolyol with 75% by weight random oxyethylene units}), with a mixturecontaining 4.86 pbw of water, 0.4 pbw of dimethylimidazole and, in caseof prepolymer 3, 0.7 pbw of silicone surfactant (SH 210, from UnionCarbide) at index 50.

The flexible foams obtained had the following properties

    ______________________________________                                                         PREPOLYMER                                                                    1      2      3                                              ______________________________________                                        Core density; kg/m.sup.3                                                                         26       26     28                                         (Iso/DIS 845)                                                                 Compression hardness, 40%; N                                                                     3.1      2.9    3.5                                        (Iso 3386/1)                                                                  Hysteresis loss; % 43       42     41                                         Tear Strength, max; N/m                                                                          169      153    193                                        (Iso/DIS 8067)                                                                Resilience; %      43       45     44                                         Compression set; %                                                            (Iso 1856, method A)                                                          Dry, 75%           21       13     14                                         Humid, 75%         46       44     34                                         ______________________________________                                    

Example 6

Rigid foams were made by reacting Suprasec VM 85 HF polyisocyanateobtainable from Imperial Chemical Industries PLC (Suprasec is atrademark of ICI) at an index of 220 with two polyol compositions(further details see Table 2, amounts in pbw). The physical propertiesof the foams are indicated in Table 2 as well.

                  TABLE 2                                                         ______________________________________                                                         Polyol   Polyol                                                               composition 1                                                                          composition 2                                       ______________________________________                                        Polyol a           29         --                                              Polyol b           35         35                                              Polyol c           25         25                                              Polyol d           8          2.15                                            Polyol e           --         34.85                                           Water              2          2                                               Tegostab B 8423, a silicone                                                                      2          2                                               surfactant from Goldschmidt                                                   trichloropropyl phosphate                                                                        10         10                                              catalyst LB from ICI                                                                             2          2                                               catalyst SFB from ICI                                                                            9.3        9.3                                             dimethyl ethanolamine                                                                            1          1                                               HCFC 141b          21         26                                              cream time, sec    12         11                                              string time, sec   37         39                                              end of rise time, sec                                                                            105        115                                             core density, kg/m.sup.3                                                                         31         31                                              Permanent Deformation under                                                                      -26        -14                                             load, %, (0.04 N/2 days/70° C.)                                        Compression strength to rise,                                                                    210        251                                             DIN 53421, kPa                                                                Dimensional stability                                                                            -0.1       0                                               (initial, -20° C., L) DIN 53431, %                                     Lambda value, (ISO 2581),                                                     mW/M.K                                                                        initial            22.1       21.0                                            after 3 weeks at 70° C.                                                                   29.4       27.5                                            Flammability test  10         12                                              B2, DIN 4102, cm                                                              ______________________________________                                         Polyol a: a polyester polyol based on diethylene glycol, glycerol, adipic     acid, glutaric acid and succinic acid having a functionality of 2.4 and a     OH value of 347 mg KOH/g.                                                     Polyol b: polyoxypropylene polyol having a functionality of 3.2 and an OH     value of 310 mg KOH/g.                                                        Polyol c: a polyester polyol based on diethylene glycol and adipic acid       having an OH value of 112 mg KOH/g.                                           Polyol d: a glycerol based polyoxypropylene polyol having an OH value of      1122 mg KOH/g.                                                                Polyol e: the polyol composition obtained in example 3.                  

We claim:
 1. Process for alcoholizing a flexible polyurethane foamcomprising:a) bringing the foam in contact with an alcoholizing polyol,allowing the foam and the polyol to react, then allowing the mixture toseparate into an upper and lower phase, subsequently collecting thesetwo phases in different containers and (b) subjecting the upper phase toan extraction process by bringing it into contact with an extractingcompound which is a polyol or a polyol mixture having a number averagemolecular weight of at most 500 and being immiscible with it, mixing theextracting compound and the upper phase, allowing the mixture toseparate into an upper phase and a lower phase and collecting these twophases, the extraction process being conducted 2-10 times batchwise orcontinuously.
 2. Process according to claim 1, wherein the flexible foamis an MDI-based, polyether polyol based, fully water blown, flexiblepolyurethane foam.
 3. Process according to claim 1, wherein thealcoholizing polyol is ethylene glycol, diethylene glycol or a mixturethereof.
 4. Process according to claim 1, wherein the reaction isconducted at a pressure ranging from ambient pressure to 10 bar, atemperature ranging from 170° to 240° C. for a period of time rangingfrom 2 to 8 hours.
 5. Process according to claim 1, wherein step (a) isconducted continuously.
 6. Process according to claim 1, wherein theamount of alcoholizing polyol ranges from 0.5-10 parts by weight perpart by weight of foam.
 7. Process according to claim 1, wherein wateris present in step (a) in an amount of up to 5% by weight calculated onthe weight of the foam and the alcoholizing polyol.
 8. Process accordingto claim 1, wherein the extracting compound is selected from the groupconsisting of ethylene glycol, diethylene glycol and mixtures thereof.9. Process according to claims 1, wherein the amount of extractingcompound is 0.5-10 parts by weight per part by weight of the upper phaseobtained according to step (a).
 10. Process according to claim 1,wherein water is present in step (b) in an amount of up to 5% by weightcalculated on the weight of extracting compound and upper phase obtainedaccording to the process (a).
 11. Process according to claim 1, whereinstep (b) is conducted at a pressure ranging from ambient pressure to 10bar, at a temperature ranging from ambient temperature to 240° C. andwherein mixing is conducted for a period of time ranging from 1 minuteto 8 hours.
 12. Process according to claim 1, wherein the extractingcompound which remains in the upper phase obtained during step (b) isremoved.
 13. Process according to claim 12, wherein said removal of theextracting compound is conducted by evaporation.
 14. Process accordingto claim 12, wherein the process is conducted continuously.
 15. Aflexible foam obtained according to a process according to claim 1.